THIN air, thick smog and bad drivers make Mexico City hard going for cyclists.

稀薄的空气、浓雾、技术奇差的驾驶员使墨西哥城中的自行车手们寸步难行。

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It's suffused with a thick smog that's a perpetual sulphur-yellow, and suffocated by motes of coal dust suspended in the breeze.

它弥漫着一层永远都是硫化黄色的浓雾，微风里浮着的煤尘微粒让人窒息。

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Thick smog that had blanketed the city Wednesday cleared, and fighter jets, helicopters and China "s first midair refueling planes flew over the center of the city."

浓厚的烟雾覆盖着周三晴朗的，有喷气式战斗机、直升机和中国空中加油机从城市中心飞过的北京城。

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Air quality in China's capital, Beijing, has once again hit serious levels, with thick smog and a sandstorm blanketing the city.

BBC: Smog and sandstorm engulf China's capital

However, China Daily says Beijing was a "city of sand and smog" yesterday after being hit by thick smog in the morning and a sandstorm in the afternoon.

BBC: China media: Mekong justice

In fact, air quality was so bad at the China Open on Thursday, October 7th, that the organizers were forced to switch the floodlights on early as thick smog drifted onto the tennis courts.

FORBES: How Green is China?